Madhu Gyawali Advisor - Dr. Pat Arnott

1. NASA-A Train Coordinated satellite measurements of the Earth’s atmosphere An overview Madhu Gyawali Advisor - Dr. Pat Arnott

2. Radiation transfer in the Earth’s atmosphere; effects of aerosols, clouds and CO2 • Afternoon constellation “A-Train” overview • Importance of formation flying • Measurements techniques like active and passive remote sensing Outline

3. Spectrum of Solar Radiation Flux • O3 • O2 • H2O • H2O • ,CO2 .1 . 3 .5 1 1.5 2 2.5 3 From Cunningham & Cunningham, 2004,

4. Major Atmospheric Windows

5. Effects Of Aerosol Direct effect —Scattering and absorption of radiation Indirect effect —Roles in cloud micro physics Clean cloud Polluted cloud Large cloud droplets Small Cloud droplets Low albedo High albedo Efficient precipitation Suppressed precipitation

6. How do Clouds Affect the Climate? Clouds Dominate the Energy Budget of the Earth Thin, high-altitude cirrus clouds emits infrared radiation Dense clouds such as cumulus and low-altitude reflect sunlight Cirrus Ice crystals Warming effect Cumulus Ice crystals/Water droplets Cooling effect Stratus Water droplets

7. Why Study CO2 ? • Since the beginning of the industrial age, the concentration of CO2 has increased by about 25%, from about 280 parts per million to over 370 parts per million. • Current research indicates that continuing increases in atmospheric CO2 may modify the environment in a variety of ways. Source: Jet Propulsion Laboratory, California Institute of Technology, Pasadena

8. Orbit Information • Orbit • Sun synchronous, polar orbit • Height -700 km • Radius - 7000 km • Inclination - 98.2o • Time • Period 98.8 minutes • Make14.57 orbits in one day • Repeat cycle 16days • Speed 7.2 km/s • All 7 members have equator crossing (ascending nodes) times 1:30 p.m.+/- 15 m • Local Time Source http://aura.gsfc.nasa.gov/instruments/index.html

9. Afternoon Constellation Evolution May 4, 2002 Madhu Gyawali Pat Arnott Source http://aura.gsfc.nasa.gov/instruments/index.html

10. Afternoon Constellation Evolution Aura(July-15) and PARASOL(Dec-18) joined in 2004 Source http://aura.gsfc.nasa.gov/instruments/index.html

11. Afternoon Constellation Evolution CloudSat and CALIPSO joined in 2006,April-28 Source http://aura.gsfc.nasa.gov/instruments/index.html

12. Afternoon Constellation Evolution Glory and OCO to be launched in 2008 Source http://aura.gsfc.nasa.gov/instruments/index.html

13. The Afternoon Constellation Is an International Undertaking Source : AMSR-E Science Team Meeting August 14-16. 2007

14. Why Fly Constellations? • Constellations opportunity • Coincident, and nearly simultaneous measurements • Field of Views overlap • Data can be correlated The new A-Train observations tell us much more about weather and climate-sensitive processes than can possibly be gleaned from any one instrument alone. The whole is greater than the sum of its parts

15. The Afternoon Constellation Is an International Undertaking

16. The Afternoon Constellation “footprints” 6x7 km POLDER 1. 4 km Cloudsat 0.5 km MODIS Band 3-7 0.09 km CALIPSO Cloud 13.5 km AIRS IR; AMSU & HSB m wave OCO 1x1.5 km 5.3 x 8.5 km TES

17. Remote Sensing Techniques for measuring or observing an object without touching. It involves the interpretation and inversion radiometric measurements of EM radiation . Example -Optical and radio telescope, camera, Atmospheric Infrared Sounder,LIDAR,RADAR Active and Passive Remote sensing

18. Remote Sensing Tools Infrared sounding ,microwave sounding RAdio Detection And Ranging LIght Detection And Ranging RADAR LIDAR Scattering of light Receiver Telescope Laser Transmitter Long wavelengths are sensitive to large particles – cloud drops, raindrops, snowflakes, hailstones Short wavelengths are sensitive to small particles –gas molecules, aerosols

19. Positions of Sensor Spaceborn Airborn Groundbased Remote sensing

20. To record detailed information from the surface for comparison with Aircraft and/or satellite remote sensing To observe the atmosphere from the ground (e.g. cloud base) Advantages • Low cost for transport and installation • Accessible for operators • Application of experimental sensors • High temporal coverage Disadvantages • Low spatial coverage • Limitations in observational area Ground Based Remote Sensing

21. Aircrafts, balloons ,helicopters Used for detailed imaging of objects or areas Satellite under flights for validation purposes Advantages • Accessible for operators • Flexibility in choosing the operation area • Higher spatial resolution than satellite resolution Disadvantages • Higher costs for transportation and installation • Less temporal and spatial coverage Airborne Remote Sensing

22. Artificial satellite ,space shuttle Advantages • Repetitive coverage of the Earth’s surface on a continuing basis • High temporal and spatial coverage (global observations) • Can observe any portion of Earth Disadvantages • Highest costs for transportation and installation • No accessible for operators • Very long preparation phase Spaceborn Remote Sensing

23. Coincident measurements of the infrared emission spectrum of the cloud free atmosphere (a) 20km looking downward over the polar ice sheet and (b) at the surface looking upward Ground Based and Airborne Coincident Remote Sensing

24. Aqua OVERVIEW Investigates the GLOBAL WATER CYCLE: evaporation from the oceans, water vapor , clouds, precipitation, soil moisture Instruments: Six earth observing instruments • AIRS: AtmosphericInfRared Sounder– Obtains highly accurate temperature profiles within the atmosphere • AMSU: Advanced Microwave Sounding Unit– Obtains temperature profiles in the upper atmosphere • HSB: Humidity Sounderfor Brazil– 4 Channel microwave sounder , measures humidity profiles throughout the atmosphere. • AMSR-E: Advanced Microwave Scanning Radiometer-Precipitation rate, cloud water, water vapor • MODIS: Moderate Resolution Imaging Spectroradiometer–Aerosol,cloud,temperature • CERES: Cloudsand the Earth's Radiant Energy System– Cloud properties, Aerosol optical depth Source http://www.nasa.gov/home/index.html

25. Measurements Frequency 750 THz 429 THz 300 GHz 0.375GHz U-violet Microwave Infrared 1 mm 0.8 m Aqua Instruments 0.4 μm 0.7 μm MODIS HSB AMSR-E • All measure electromagnetic radiation • All are passive instruments i.e. they simply record • radiation coming to them CERES AMSU-A2 AMSU-A1 AIRS Aqua covers wide range of Earth science UV + VISIBLE + IR + Microwave Hurricane Katrina approaching the Gulf Coast Source http://www.nasa.gov/home/index.html Aug. 28th 2005, MODIS

26. Aura The Aura satellite provides us the first global view of the Earth's atmosphere. TES Nadir view Limb View Instruments Source http://aura.gsfc.nasa.gov/instruments/index.html • HIRDLS: HIgh Resolution Dynamics Limb Sounder– global distribution of temperature and composition of the atmosphere • MLS: Microwave Limb Sounder –stratospheric temperature and upper tropospheric constituents • OMI : Ozone Monitoring Instrument– Distinguishes between aerosol types, tropospheric ozone. • TES: Tropospheric Emission Spectrometer – all radiatively active molecular species in the Earth's lower atmosphere.

27. Measurements HIRDLS in yellow, OMI(has a cross track swath of 2600km) in blue, MLS in green, and TES in red. Source http://aura.gsfc.nasa.gov/instruments/index.html

28. PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Science coupled with Observations from a LIDAR) Measures radiative and microphysical properties of clouds and aerosols by measuring the directionality and polarizationof light reflected by the earth-atmosphere-ocean system Instrument • POLDER (POLarization and Directionality of the Earth’s Reflectance) • A rotating wheel scans 9 wavelength bands(443-1029 nm) • A target is viewed up to 16 times with various viewing angles • Three of the channels (490,670,865 nm) also measures linear polarization,Lidar 1064 nm 532 nm Source: CNES

29. Measurements • Polarization distinguishes the liquid phase clouds and ice-phase clouds ,as the former has strong peak of polarization • The cloud level pressure (or altitude)is measured by using the differential absorption technique • PARASOL can discriminate large spherical marine aerosols from non-spherical desert aerosols PARASOL first images over Europe (2005 January):natural(left) and polarized(right)

30. CALIPSO Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations Three instruments • CALIOP : Cloud-Aerosol Lidar with Orthogonal Polarization - Two wavelength polarization-sensitive Lidar (532 and 1064 nm) that provides high-resolution vertical profiles of aerosols and clouds • WFC:Wide Field Camera - Fixed, nadir-viewing imager with a spectral channel covering the 620-670 nm region • IIR: Imaging Infrared Radiometer - Nadir-viewing, non-scanning imager

31. Measurement 30 CALIPSO’s polarization lidar instrument can detect aerosol Particles and can distinguish between aerosol and cloud particles Altitude km 0 The orange and red colors signify regions of fine aerosols – that suspended above Earth’s surface.

32. CloudSat • Measures the power backscattered by clouds as a function of distance from the radar. Instruments • CPR: Cloud Profiling Radar - A 94-GHznadir-looking radar • Will advance our understanding of cloud abundance, distribution, structure, and radiative properties. • Able to detect the much smaller particles of liquid water and ice (ground-based weather radars use centimeter wavelengths) Tight formation flying of CALIPSO and CloudSat- seperated by 15 s Cloud Profiling Radar

33. Measurements Radar measures the time delay and magnitude of the reflected signal A fraction of these pulses reflect back while others continue downward, some being absorbed CALIPSO +CLOUDSAT MISSION CALIPSO and CloudSat will provide the first statistics on the vertical structure of clouds. For the first time ,we will see clouds from their tops to their bottoms-like getting CT scan of clouds from space Provide the first validated estimate of how much clouds and aerosols contribute to the vertical distribution of atmospheric warming

34. Future Missions Schedule date: Dec-15,2008 • OCO: OrbitingCarbonObservatory • Will make first space based measurements of column CO2 to quantify sources and sinks of CO2 • Instrument • Three grating spectrometers to measure at 2.06um and 1.61um,and 760nm for the Oxygen A-band . OCO Glory Source: Jet Propulsion Laboratory, California Institute of Technology, Pasadena

35. Glory Launch Date: December 2008 Launch Site: Vandenberg AFB, California • Will make the measurements of the Earth's energy balance and the effect of black carbon soot and other aerosols in the atmosphere • Instrument • Aerosol Polarimetry Sensor -continuous scanning sensor that collect visible, near infrared, and short-wave infrared data scattered from aerosols and clouds. • Total Irradiance Monitor(TIM)will collect high accuracy, high precision measurements of total solar irradiance • Will measure the total solar irradiance to determine the Sun's direct and indirect effect on the Earth's climate.

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37. Summary • Sun synchronous satellites have many advantages than other satellites like geo stationary, as they offer higher resolution, carry many instruments and can observe at many more wavelengths. • The A-Train formation allows for coordinated and coincidence measurements. Also there are several complementary differences among the way the different instruments in the constellation observe the same object or process. • New data from NASA's A-Train constellation, coupled with recent advances in climate modeling, creates a rare opportunity to advance understanding of the interaction of atmospheric constituents and their climate consequence

38. THANK YOU

39. ABSTRACT The “NASA-A Train“ constellation of seven Earth–orbiting satellites remotely sense Clouds , aerosols, water vapor, and trace gases such as CO2,NO2, and O3. The satellites orbit sun –synchronously at an altitude of 705 km with Aqua in the lead ,followed in order by CALIPSO,CloudSat,PARASOL,and Aura. With Aqua in the lead and Aura at the tail this formation has been termed the afternoon constellation or A-Train, and all satellites cross the equator within a few minutes around 1:30 pm local time. These satellites employ revolutionary measurement methods to probe the Earth’s atmosphere, and will improve our weather and climate forecasts. Data from these satellites can be used together to obtain comprehensive information about atmospheric processes. This talk will give an over view of the active and passive remote sensing.Measurement techniques used on satellite as well as description of the importance of the atmospheric properties being measured. A discussion will be presented on the importance of synergistic measurements of satellite suite.